Properties of wheat dough at sub-zero temperatures and freeze tolerance of a baker's yeast (Saccharomyces cerevisiae)

This work studied the relationship between the freeze tolerance of a baker's yeast (Saccharomyces cerevisiae) and the physical properties of the frozen wheat dough. The behavior of wheat dough, of the gluten phase, and of the liquid phase at sub-zero temperatures was examined by differential scanning calorimetry (DSC) and cryomicroscopy. The effect on yeast viability of dough water content, freezing and storage temperatures, and prefermentation before freezing was studied. Yeast viability was mostly affected by the freezing and storage temperatures, with temperatures below the glass transition temperature (T-g) giving the highest survival ratios. At temperatures above T-g, viability after freezing treatment and during storage seemed to be governed by different mechanisms, encompassing osmotic and mobility factors. Those factors were also found to influence the freeze tolerance of growing yeast in the presence of ethanol.